The present invention relates to the field of communication along a drill string used for oil and gas exploration, and particularly to the area of interfacing with a network along a drill string. Communication with downhole tools while drilling has been sought for several decades. Several systems in the prior art have disclosed communication with downhole equipment, and for purposes of understanding they may be grouped into two categories: those that communicate along a wireline cable, and those that communicate through a tool string
Examples of systems which communicate along a wireline cable may be found in U.S. Pat. No. 5,521,592 to Veneruso (the '592 patent) and U.S. Pat, No. 5,140,318 to Stiner (the '318 patent). The '592 patent discloses a method and apparatus for transmitting information, in which information picked up by at least one downhole sensor is conveyed to surface reception means via a wire connection electrically connecting said device to an electrical power supply means on the surface, said wire connection is inductively coupled firstly with said sensor and secondly with said reception means. The '318 patent discloses a data transmission system for use with a logging cable that functions to provide a more precise transmission of data signal with reduced interference from higher-powered electrical signals present along the line. The data signals are modulated on a radio frequency carrier, which is then inductively coupled to the cable jacket or shielding sheath for conduction along the cable.
Examples of systems that communicate through a tool string are disclosed in U.S. Pat. No. 6,679,332 to Vinegar (the '332 patent), and U.S. patent application Ser. No. 10/905,894 filed on Jan. 25, 2005 in the name of Hall et. al (The '894 application). The '332 patent discloses an electronic module that communicates with the surface using the tubing string and casing as conductors. Induction chokes at the surface and downhole electrically impede AC flow through the tubing with a resulting voltage potential useful for power and communication. The '894 application discloses a communication element electrically connected with a transmission path within a downhole component that inductively communicate with electronic equipment.